One approach to securely licensing a device relies on encoding data in different parts of a license key. If the scheme is uncovered, the license key could be generated by others including unlicensed individuals.
Another approach is to require users to register their products online with a license key included with the product. Product software then performs a network-based check to determine if the product is licensed. A user of the product needs to maintain or establish a network connection on a recurring basis in order to allow license determination of the product. Further, the value of the license cannot be recovered once used for a particular product as no way to prove that the license was removed exists.